LadyMom just posted this link about food allergies, it's great:
Only Natural Pet Store - Dogs Cats Holistic Supplies Products Food Treats Vitamins Medicine Supplements
This is one for pet allergies, overall, that I like too:
Pet Care Library: Allergies in Dogs
If you switch to a new food, just make sure you're choosing a novel protein (one she hasn't eaten before). Omega 3s can be helpful in dogs w/ allergies - the vet derms we've seen say they are worth a try.
So, she does itch all year round then? Not worse during pollen season?